The present invention generally relates to a rotating spray dryer atomizer wheel to be positioned in a treatment chamber for use in connection with flue gas desulfurization, and in particular relates to an improved lid and upper wear ring system for such an atomizer wheel.
Flue gas desulfurization systems are typically used in coal fired power plants, waste-to-energy plants and in incinerators. A typical desulfurization system will include a processing or treatment chamber wherein flue gasses are subjected to desulfurization treatment. Positioned inside that chamber is a high speed rotating atomizing wheel or head through which a desulfurization treatment slurry is dispersed into the chamber and the gas therein in order to initiate the desulfurization process. Such a desulfurization system might typically be powered by drive systems that include motors in the 160 to 1100 horsepower range that rotate the atomizing heads at speeds of 8,800-10,000 rpm and upwards to 15,000 rpm. While these heads are rapidly rotating at these very high speeds, a slurry treatment mixture, typically of water, lime and fly ash of upwards to 20%-40% solids, is fed into the heads at rates ranging typically between 20-150 gallons per minute. Due to the rotational velocity of the heads, the slurry fed into the heads is accelerated and expelled through nozzles positioned around the circumference of the rotating heads into the treatment chamber. The atomized mist of the treatment slurry chemically reacts with the sulfur in the flue gasses to form solid particles that precipitate from the flue gas. These solid partiuclates formed from the chemical reaction of the atomized treatment slurry and the flue gasses are filtered out, thereby removing the sulfur from the flue gas.
An apparatus typical of the type of atomizing head or wheel that is the subject of the improvement of the present is shown in U.S. Pat. No. 5,370,310. Atomizer wheels of a similar type are also disclosed in U.S. Re. Pat. No. 30,966, U.S. Re. Pat. No. 30,963 and U.S. Pat. No. 5,356,075. In each of the atomizers disclosed in these patents, the atomizer wheels are circular with a circumferential sidewall that forms a hollow center or annular space. Nozzle openings project through the circumferential sidewall. A lid or cover plate fits over the annular space. In the lid is an opening or inlet through which slurry to be atomized passes into the annular space. The atomizer wheel is positioned within a treatment chamber wherein atomized slurry from the wheel reacts with the gasses in the chamber to desulfurize the gasses. Similar atomizer heads are also used in spray dryers for drying certain clays and mild solids.
In these prior atomizer wheels, the lids to the wheels are essential components of the wheel assemblies and are supplied as original equipment with the wheels. The lids are usually comprised of stainless steel or other materials such as titanium and hastelloys. A serious problem arises as a result of the flow of slurry materials into the wheel through the opening in the lid. The lid surface at the opening wears due to the slurry materials being forced there against, and the lid surface usually does not wear equally or concentrically around the opening. This wearing of the opening in the lid, and in particular the uneven wear, causes the lid to deteriorate, and the uneven nature of the wearing causes the wheel to have a balance problem at the high rotation speeds that the wheel operates under. Under these circumstances, even though the atomizer head itself and the nozzle components may wear well, it becomes frequently necessary to replace the stainless steel or other alloy material lid in order to compensate for this particular wear. Replacement of these lids is expensive: the lids themselves are expensive, and the down time of the treatment apparatus associated with removing the atomizer and replacing the lid is a further expense that must be considered. Operation of these scrubbing systems is critical to air quality, and any down time that can be eliminated or at least reduced results in overall savings.
In order to overcome the shortcomings associated with these prior types of lids associated with the atomizer heads, there have been attempts made to try to decrease wear at the inlet opening and thus increase the lid life. One prior attempt to compensate for wear at the lid inlet has been to coat the inlet opening with a layer of hardened material. In one particular attempt, multiple spray coatings of a wear-resistant material, for example tungsten carbide or chrome carbide material, were applied to the inlet opening to a thickness of approximately 0.050xe2x80x3 to 0.060xe2x80x3. Even though these spray coatings increased the wear life of the lid at the inlet opening significantly, the life expectancy of the lid was still considered inadequate.
Another problem closely associated with the atomizer lid construction of the types generally associated with these slurry atomizers involves slurry penetration into the o-ring groove area underneath the rim of the lid. As will be discussed in greater detail hereinafter, as the lid begins to wear, the injected slurry, due to the high centrifugal forces created within the rapidly rotating head, begins to flow or be urged past the rim of the lid into the area between the wear rings and the lid. The build up of slurry in this area can eventually cause the very brittle wear rings to crack since they do not tolerate bending very well. When this happens, not only does the worn lid need to be replaced, the associated wear ring must be replaced as well, adding further to the cost of maintenance and repair of the atomizer.
Because of these inherent deficiencies in the lid construction, lids that should have a lifespan of a number of years in reality have lifespans of a matter of months. The same is true of the life of the associated wear ring.
It is, therefore, desirable to provide an improved lid for the atomizer wheel or head that has superior wear qualities at its inlet opening through the lid. Furthermore, such an improved lid should be easy to substitute for the original equipment lid and at the same time provide a confirguration that will protect its associated wear ring so that the wear ring is secure from premature failure through breaking due to slurry penetrating between the wear ring and the lid.
A lid assembly is disclosed for a rotatable atomizer wheel with an atomizing chamber for the receipt of a slurry through the lid assembly. The lid assembly includes a lid member adapted to fit onto the rotatable atomizer wheel over the atomizing chamber. The lid member has an first opening there through directed into the atomizing chamber when the lid member is positioned on the atomizer wheel. In addition, the lid assembly includes a wear ring for protecting the exposed surface of the first opening through said lid member from slurry flowing through the lid. This wear ring is fitted inside and extends through the first opening through the lid member and has a second opening there through into the atomizing chamber, so that when the lid member with the wear ring fitted therein is positioned on the atomizer wheel there is an opening through to the atomizing chamber. The material of the wear ring has a greater wear resistance than the material of the lid member.